1. Field of the Invention
The present invention relates to flexible microsurgical instruments. In particular the present invention relates to flexible microsurgical instruments having a distal portion which is ground to a reduced diameter and fitted with a stiffening sleeve.
2. State of the Art
Flexible microsurgical instruments, in particular endoscopic biopsy forceps, are used for taking tissue samples from the human body for analysis. These instruments typically have a long flexible coil containing one or more control wires coupled to a proximal actuating handle. The actuating handle moves the control wires relative to the coil to effect a tissue sampling operation at the distal end of the coil. A pair of forceps jaws are mounted on a clevis at the distal end of the coil. The forceps jaws are coupled to the control wires so that movement of the control wires causes the jaws to open and close to bite a tissue sample.
The endoscopic biopsy procedure is accomplished through an endoscope which is inserted into a body and guided by manipulation to the biopsy site. The endoscope typically includes a long narrow flexible tube with an optical lens and a narrow lumen for receiving a biopsy forceps. The practitioner guides the endoscope to the biopsy site while looking through the optical lens and inserts the biopsy forceps through the lumen of the endoscope to the biopsy site. While viewing the biopsy site through the optical lens of the endoscope, the practitioner manipulates the actuating handle to effect a tissue sampling operation at the distal end of the instrument. The practitioner must align the open jaws with the tissue to be sampled so that upon closing the jaws, a portion of the tissue is trapped between the jaws. It is a known problem with biopsy forceps that as the jaws are closed the distal end of the flexible coil deflects because the force applied at the actuating handle to the control wires is transferred to the distal end of the flexible coil. The deflection of the distal end of the coil just as the jaws are about to close on a tissue to be sampled often displaces the jaws relative to the tissue to be sampled and results in a failure to acquire the sample or the acquisition of an undesired sample. Therefore it is desirable to stiffen the distal portion of the coil to prevent it from deflecting when the jaws are being closed.
Grandparent U.S. Pat. No. 5,228,451 to Bales et al. discloses a biopsy forceps device having a stiff distal portion. The distal portion of the flexible coil is made stiff by wrapping it with a stiffening sleeve which extends for several inches along the coil and covers a portion of the clevis. The sleeve effectively stiffens the distal portion of the coil, but also increases the outer diameter of the coil. Moreover, the change in outer diameter of the coil where the sleeve begins and ends results in a less than smooth outer surface which might hinder travel of the instrument through the narrow lumen of the endoscope and might cause additional wear to the endoscope.